How to Remove a (really) Difficult Subfloor

December 22, 2018

Long wedges cut from 2x4s are extremely effective for removing difficult flooring. Oh yeah, and don't forget the sledgehammer.

Since ceramic tile started to replace linoleum as bathroom and kitchen floor covering 20-25 years ago, many remodeling projects I encounter these days involve tearing up out-of-date ceramic tile. The materials and methods used in those early days can be a REAL challenge to undo because tile installers often went with the 'more is better' approach to insure a callback-free installation.

On the project featured here it turned out that the tile was firmly stuck to the underlayment plus the 3/4" thick underlayment was thoroughly glued and screwed down to the subfloor. The remodel included reconfiguration/relocation of the toilet and shower as well as the associated water and drain piping alterations.

The crawlspace below the bathroom is essentially inaccessible, unfit for man or beast (although it is quite fit for various vermin and pestilence) so I knew I'd have to cut access holes in the subfloor which meant first removing the tile and underlayment.

I hoped that removing underlayment would just be a matter of using a couple prybars to pop it loose ... NOT!

Demolition Math: (wedges + sledgehammer) > (hammer + prybar)

When the hammer and prybar weren't tough enough to tear up the glued and screwed 3/4 inch A/C plywood underlayment, I moved to 'Plan B.' Plan B is pretty straightforward: cut a batch of long, tapered 'wedges' from 2x4's to drive under the subfloor with a small sledgehammer. It is amazing how effective this simple process is for the toughest jobs!

How to do it:

Cut enough wedges out of dense 2x4's with minimal knots to space them out at 12 inch to 18 inch intervals along the edge of subfloor being removed. You'll need more wedges with a longer taper for the toughest jobs, fewer wedges with shorter tapers for easier tear-ups.

Using a steel prybar lift the underlayment to start the thin, fragile ends of the wood wedges.

Consume copious quantities of Wheaties, Red Bull or biscuits and gravy to carbo-load appropriately for the task ahead.

Drive wedges sequentially with a few whacks each for best results, going back and forth across them.

Continue with additional wedges for difficult conditions.

Remove lifted sections as they become freed up from glue and fasteners.

Ironically, on this job the underlayment was attached to the subfloor WAY better than the subfloor was attached to the floor joists. And as you can see at the end of the video the subfloor was seriously compromised when the underlayment peeled up two and three layers top layers of veneer.

What doesn't show up is that the subfloor was attached with just five 1/2" crown staples in each joist (!). Some joists had only a hinky dab of 35 year-old construction adhesive and NO fasteners.

On one butt-joint in the subfloor, the staples were neatly driven right into the crack between the sheets! So after all the drama of separating the subfloor from the underlayment I ended up cutting the subfloor out of the whole room and installing a new layer of 3/4" plywood complete with polyurethane construction adhesive and 1-3/4 inch torx-drive screws.

As it turned out if I'd just popped up the tile by the time I got done cutting holes for relocating the plumbing the floor would have looked like a plywood quilt and I would have gone through all the same steps anyway—which, considering how tough the job turned out to be, is good to know that the time, effort, and expense was not wasted.

I do have a pang of remorse for the poor fella who will end up tearing out this tile 20-25 years hence when interior designers create a resurgence of paisley-patterned linoleum for residential bathrooms.

Extra Credit:

This method can be adapted for a wide range of applications; it is excellent for removing hardwood flooring, for example. In fact, with a 'careful touch' using very long tapered wedges, it is the best approach for removing hardwood flooring for salvage, preservation and re-use because tongue and groove edges are preserved with the forceful—yet gradual—lifting generated by the wedges.

—Matt Jackson is a master carpenter, remodeler, SketchUp Wiz, YouTuber, and contributing editor to ProTradeCraft. He lives and works in Rapid City, South Dakota.